1. Biological molecules: Carbohydrates 1 - Simple sugars
- Created by: Lois
- Created on: 05-04-13 20:25
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- Carbohydrates 1: Simple sugars
- Carbohydrates in living organisms
- Carbohydrates make up about 10% of the organic matter of a cell
- The functions of carbohydrates include: energy source - released from glucose during respiration, energy store e.g. starch and structure e.g. cellulose
- Some carbohydrates also form part of larger molecules e.g. nucleic acids, glycolipids
- Carbohydratescontain the elements carbon, hydrogen and oxygen. The term carbohydrate essentially means 'hydrated carbon', because the elements are found in the proportions Cn(H2O)n
- Some carbohydrates also form part of larger molecules e.g. nucleic acids, glycolipids
- For every carbon present in a carbohydrate, the equivalent of a water molecule is also present
- Simple sugars
- The simplest carbohydratesare called the monosaccharides.
- These are the monomers (basic units) of carbohydrates, all larger carbohydratesare made by joining monosaccharides together
- Monosaccharides containing 3-6 carbons have very similar properties: soluble in water, sweet tasting and forms crystals
- Monosaccharides are grouped according to their number of carbon atoms, 3-carbon: triose sugars, 5-carbon: pentose sugars, 6-carbon: hexose sugars
- Most common: hexoses, these include glucose & fructose. One H2O for every carbon so written as C6H12O6, pentoses and hexoses tend to occur in nature as ring structures
- The simplest carbohydratesare called the monosaccharides.
- Two forms of glucose
- Glucose can be drawn as a chain or ring structure, the ring structure can be shown 2 different ways: the H & OH at cabon1 may be above or below the plane of the ring
- In alpha-glucose the OH at C1 is below the plane; in beta-glucose the OH at C1 is above the plane
- The different structures lead to different chemical properties when joined to form polysaccharides
- Joining monosaccharides and splitting disaccharides
- Two monosaccharide molecules can be joined in a condensation reaction, forming a disaccharide
- A new covalent glycosidic bond forms and water is eliminated
- The reverse hydrolysis reaction uses a water molecule to break the glycosidic bond
- e.g. sucrose = alpha glucose + fructose
- Building the polysaccharides starch, glycogen and cellulose and breaking down larger molecules involves the making and breaking of glycosidic bonds
- Carbohydrates in living organisms
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